ENS 53793
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ENS Event | |
|---|---|
06:00 Dec 18, 2018 | |
| Title | Automatic Reactor Trip - Loss of Non-Vital Bus |
| Event Description | On December 18, 2018 at 1126 CST, Arkansas Nuclear One, Unit 1 (ANO-1) reactor automatically tripped due to a loss of the A-1, non-vital 4160V bus. All control rods fully inserted. Loss of the A-1 bus resulted in de-energizing A-3 vital 4160V bus. Emergency Diesel Generator #1, K-4A, started automatically and is currently powering A-3 vital bus. Non-vital buses A-2, H-1, and H-2 and vital bus A-4 transferred power automatically to the Startup Transformer #1. Off-site power remains energized and available for ANO-1. The reason for loss of A-1 bus is unknown at this time. Currently, ANO-1 has stabilized in Mode 3, Hot Standby.
Decay heat is being removed by the main condenser using the turbine bypass valves. The loss of the A-1, non-vital bus, is under investigation. The licensee has notified the NRC Resident Inspector and the state. |
| Where | |
|---|---|
Arkansas Nuclear  Arkansas (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.72(b)(2)(iv)(B), RPS Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | |
| Time - Person (Reporting Time:+9.67 h0.403 days <br />0.0576 weeks <br />0.0132 months <br />) | |
| Opened: | Sean Davis 15:40 Dec 18, 2018 |
| NRC Officer: | Dong Park |
| Last Updated: | Dec 18, 2018 |
| 53793 - NRC Website | |
Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | A/R |
| Before | Power Operation (100 %) |
| After | Hot Standby (0 %) |
Arkansas Nuclear with 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation | |
WEEKMONTHYEARENS 563512023-02-14T17:03:00014 February 2023 17:03:00
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Non-Vital Bus ENS 534592018-06-16T05:00:00016 June 2018 05:00:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Reactor Trip During Startup ENS 534042018-05-16T22:50:00016 May 2018 22:50:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Trip Due to Loss of Main Feedwater Pump ENS 527102017-04-26T15:04:00026 April 2017 15:04:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Unit 1 Automatic Reactor Scram Due to Partial Loss of Offsite Power ENS 516072015-12-15T11:44:00015 December 2015 11:44:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release, 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Reactor Trip Due to Loss of Feed to One Steam Generator ENS 500632014-04-28T01:12:00028 April 2014 01:12:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Trip Due to an Auxiliary Trip on Core Protection Calculator ENS 499952014-04-03T18:01:0003 April 2014 18:01:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Trip ENS 496182013-12-09T14:00:0009 December 2013 14:00:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release, 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(a)(1)(i), Emergency Class Declaration, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Unusual Event Declared Due to Unit 2 Auxiliary Transformer Explosion ENS 488692013-03-31T15:33:00031 March 2013 15:33:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release, 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(a)(1)(i), Emergency Class Declaration, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Notification of Unusual Event Declared Due to a Breaker Explosion in the Protected Area ENS 481692012-08-08T13:23:0008 August 2012 13:23:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Trip Due to High Reactor Coolant System Pressurizer Pressure ENS 458722010-04-26T05:00:00026 April 2010 05:00:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Unit 1 Experienced an Automatic Reactor Trip During an Ni Calibration ENS 458542010-04-18T18:57:00018 April 2010 18:57:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Manual Reactor Trip During Reactor Startup ENS 455492009-12-08T14:42:0008 December 2009 14:42:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Reactor Trip Due to Low Steam Generator Level Caused by Loss of Main Feed Water Pump ENS 453672009-09-20T10:11:00020 September 2009 10:11:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Unplanned Emergency Diesel Auto Start During Surveillance Testing ENS 449062009-03-14T02:51:00014 March 2009 02:51:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release, 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Feedwater Regulating Valve Failure Leads to Manual Reactor Trip ENS 448372009-02-07T16:59:0007 February 2009 16:59:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(a)(1)(i), Emergency Class Declaration Unusual Event Declared Due to a Fire Onsite ENS 448312009-02-05T21:24:0005 February 2009 21:24:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Unit 1 Manually Tripped Due to Control Rod Drive Motor High Temperatures ENS 447362008-12-20T18:12:00020 December 2008 18:12:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Manual Reactor Trip When Control Rod Bank Inserted Without Operator Action ENS 447162008-12-12T14:55:00012 December 2008 14:55:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Unit 1 Was Manually Tripped from 32% Power Due to an Abnormal Rod Pattern ENS 441252008-04-07T18:45:0007 April 2008 18:45:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Core Element Assembly Calculators Declared Inoperable ENS 422292005-12-26T16:47:00026 December 2005 16:47:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Trip Following Turbine Trip ENS 401192003-08-29T19:28:00029 August 2003 19:28:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Trip on High Rcs Pressure 2023-02-14T17:03:00 | |
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